A procedure for determining the effective thickness of non-uniform irregular-shaped samples via radiative capture is described. In this technique, partial γ-ray production cross sections of a compound nucleus produced in a neutron-capture reaction are measured using Prompt Gamma Activation Analysis and compared to their corresponding standardized absolute values. For the low-energy transitions, the measured cross sections are lower than their standard values due to significant photoelectric absorption of the γ rays within the bulk-sample volume itself. Using standard theoretical techniques, the amount of γ-ray self absorption and neutron self shielding can then be calculated by iteratively varying the sample thickness until the observed cross sections converge with the known standards. The overall attenuation, thus, provides a measure of the effective sample thickness illuminated by the neutron beam. This procedure is illustrated through radiative neutron capture using powdered oxide samples comprising enriched ¹⁸⁶W and ¹⁸²W from which their tungsten-equivalent effective thicknesses are deduced to be 0.077(3) mm and 0.042(8) mm, respectively.

A stacked-target of natural lanthanum foils (99.9119% 139La) was irradiated using a 60 MeV proton beam at the LBNL 88-Inch Cyclotron. 139La(p,x) cross sections are reported between 35–60 MeV for nine product radionuclides. The primary motivation for this measurement was the need to quantify the production of 134Ce. As a positron-emitting analogue of the promising medical radionuclide 225Ac, 134Ce is desirable for in vivo applications of bio-distribution assays for this emerging radio-pharmaceutical. The results of this measurement were compared to the nuclear model codes TALYS, EMPIRE and ALICE (using default parameters), which showed significant deviation from the measured values.

We have deduced the emission probability of the 447-keV γ ray from the ϵ+β+ decay of Ceg137 (9.0 h) relative to that of the 254-keV γ ray from the Cem137 (34.4 h) decay in transient equilibrium. The time-dependent factor in transient equilibrium was applied following the Bateman equation for a radioactive decay chain. The isotope was produced via the La139(p,3n)Cem,g137 reaction by bombarding natLa with a proton beam from the 88-in. cyclotron at Lawrence Berkeley National Laboratory. γ-ray intensities were measured using an HPGe detector. The emission probability for the 447-keV γ ray deduced in this work is 1.21(3) (that is 1.21 ± 0.03) per hundred parent decays, which differs significantly from an earlier published value of 2.24(10). We identify the source of this discrepancy to be an incorrect use of the time-dependent factor. Additionally, we have deduced the emission probability of the 504-keV γ ray from the decay of Yg85 (2.68 h) relative to that of the 232-keV γ ray from the Srm85 (1.127 h) decay in transient equilibrium. The isotope was produced via the Sr86(p,2n)Yg85 reaction by bombarding SrCO386 with a proton beam at the same facility. The study confirms the assumption of the time-dependent correction for recommending the emission probability of the 504-keV γ ray in the literature. Our work highlights the importance of explicit description by authors of any time-dependent correction they have made when reporting γ-ray intensities for nuclides in transient equilibrium. The need and significance of accurate and precise decay data of Ceg137 and Yg85 in basic science and medicine is briefly outlined.

Cross sections for the 47Ti(n,p)47Sc and 64Zn(n,p)64Cu reactions have been measured for quasi-monoenergetic DD neutrons produced by the UC Berkeley High Flux Neutron Generator (HFNG). The HFNG is a compact neutron generator designed as a “flux-trap” that maximizes the probability that a neutron will interact with a sample loaded into a specific, central location. The study was motivated by interest in the production of 47Sc and 64Cu as emerging medical isotopes. The cross sections were measured in ratio to the 113In(n,n′)113mIn and 115In(n,n′)115mIn inelastic scattering reactions on co-irradiated indium samples. Post-irradiation counting using an HPGe and LEPS detectors allowed for cross section determination to within 5% uncertainty. The 64Zn(n,p)64Cu cross section for 2.76-0.02+0.01 MeV neutrons is reported as 49.3 ± 2.6 mb (relative to 113In) or 46.4 ± 1.7 mb (relative to 115In), and the 47Ti(n,p)47Sc cross section is reported as 26.26 ± 0.82 mb. The measured cross sections are found to be in good agreement with existing measured values but with lower uncertainty (<5%), and also in agreement with theoretical values. This work highlights the utility of compact, flux-trap DD-based neutron sources for nuclear data measurements and potentially the production of radionuclides for medical applications.

A set of prompt partial γ-ray production cross sections from thermal neutron capture were measured for the La139(n,γ) reaction using a guided beam of subthermal (thermal and cold) neutrons incident on a La2natO3 target at the Prompt Gamma Activation Analysis facility of the Budapest Research Reactor. Absolute La140 cross sections were determined relative to the well-known comparator Cl35(n,γ) cross sections from the irradiation of a stoichiometric LaCl3nat sample. The total cross section for radiative thermal neutron capture on La139 from the sum of experimentally measured cross sections observed to directly feed the La140 ground state was determined to be σ0expt=8.58(50) b. To assess completeness of the decay scheme and as a consistency check, the measured cross sections for transitions feeding the ground state from levels below a critical energy of Ec=285 keV were combined with a modeled contribution accounting for ground-state feeding from the quasicontinuum to arrive at a total cross section of σ0=9.36(74) b. In addition, a neutron-separation energy of Sn=5161.001(21) keV was determined from a least-squares fit of the measured primary γ-ray energies to the low-lying levels of the La140 decay scheme. Furthermore, several nuclear structure improvements are proposed for the decay scheme. The measured cross-section and separation-energy results are comparable to earlier measurements of these quantities.

Cross sections of proton-induced nuclear reactions on enriched 86Sr target were measured by the activation technique up to proton energies of 44 MeV. The isomeric cross-section ratios for 86 m , gY and 85 m , gY as a function of projectile energy were deduced from their measured data. The present experimental data for the nuclear reaction products, namely 86 mY, 86 g + xmY, 85 mY, 85 gY, 84Rb and 83Rb were compared with the results of nuclear model calculations using the code TALYS, which combines the statistical, precompound, and direct interactions. In general, the experimental cross-section data as well as the isomeric cross-section ratios are reproduced well by the model calculations, provided the input model parameters are properly chosen and the level structure of the product nucleus is thoughtfully considered. The quality of the agreement between experimental data and model calculations was numerically quantified. For products formed via emission of a light complex particle as well as multi-nucleons (e.g., α and 2p2n), the contribution of the latter process starts increasing when its energy threshold is crossed.

The nuclear reactions C12(C12,α)Ne20, C12(C12,p)Na23, and C12(C12,n)Mg23 are the primary reactions in carbon burning, which occurs as part of several stellar processes. The Gamow window, which describes the energy range where most of these reactions take place, is typically around 1.5 MeV in the center-of-mass frame. Direct measurements of the cross sections at this energy are difficult due to the large Coulomb barrier present between the carbon nuclei; however, a successful surrogate measurement can provide the branching ratios between these reactions while avoiding the C12+C12 Coulomb barrier. An experiment was performed using inelastic scattering of 40 MeV α particles on Mg24 as a possible surrogate for the C12+C12 compound nucleus.

The neutron-capture reaction is fundamental for identifying and analyzing the γ-ray spectrum from an unknown assembly because it provides unambiguous information on the neutron-absorbing isotopes. Nondestructive-assay applications may exploit this phenomenon passively, for example, in the presence of spontaneous-fission neutrons, or actively where an external neutron source is used as a probe. There are known gaps in the Evaluated Nuclear Data File libraries corresponding to neutron-capture γ-ray data that otherwise limit transport-modeling applications. In this work, we describe how new thermal neutron-capture data are being used to improve information in the neutron-data libraries for isotopes relevant to nonproliferation applications. We address this problem by providing new experimentally-deduced partial and total neutron-capture reaction cross sections and then evaluate these data by comparison with statistical-model calculations.

A segmented Si-telescope and HPGe array, STARS-LIBERACE, was used to study the 156Gd(p, tγ)154Gd direct reaction by particle- γ coincidence spectroscopy. New cross sections with a 25MeV proton beam are reported and compared to previous (p,t) and (t,p) studies. Furthermore, additional evidence for coexisting Kπ=01+,21+ and 02+, 22+ configurations at N = 90 is presented. Direct and indirect population patterns of the low-lying states are also explored. Review of the new and existing evidence favors an interpretation based on a configuration-dependent pairing interaction. The weakening of monopole pairing strength and an increase in quadrupole pairing strength could bring 2p-2h 0 + states below 2 Δ. This may account for a large number of the low-lying 0 + states observed in two-nucleon transfer reactions. A hypothesis for the origin of the 02+ and 03+ states is provided.

The emission of γ rays from neutron-bound and neutron-unbound states in Mo95, populated in the Mo94(d,p) reaction, has been investigated. Charged particles and γ radiation were detected with arrays of annular silicon and Clover-type high-purity Germanium detectors, respectively. Utilizing p-γ and p-γ-γ coincidences, the Mo95 level scheme was greatly enhanced with 102 new transitions and 43 new states. It agrees well with shell model calculations for excitation energies below ≈2 MeV. From p-γ coincidence data, a new method for the determination of spins of discrete levels is proposed. The method exploits the suppression of high-angular momentum neutron emission from levels with high spins populated in the (d,p) reaction above the neutron separation energy. Spins for almost all Mo95 levels below 2 MeV (and for a few levels above) have been determined with this method.